Lockheed P-58 Chain Lightning

Introduction

The Lockheed P-58 Chain Lightning is almost a textbook example of what changing requirements, military mismanagement, and vacillating officialdom can do to a promising military aircraft project. The XP-58 started life as a fairly straightforward development of the P-38 Lightning fighter, evolved in stages into an escort fighter, then into an attack plane, then into a bomber, then into a tank buster, and then finally into a bomber destroyer. It went from a single-seater to a two-seater and then back to a single seat aircraft again. These incessant changes in requirements, combined with several changes in power plants, resulted in the XP-58, which started life in 1940, being delayed until nearly the end of the war.

Early Development

The USAAC granted authorization to export the unturbosupercharged Lightning to Britain and France, but only under the condition that Lockheed agree to develop and produce at no cost to the U.S. government a prototype of an advanced version of the Lightning. The formal agreement was signed on April 12, 1940. This advanced Lightning was given the company designation of L-121.

The L-121 was to be powered by a pair of turbosupercharged Continental IV-1430 liquid-cooled engines. It was to be offered in two versions, a single- seater and a two-seater. The single-seat version was to retain the standard P-38 armament of one 20-mm cannon and four 0.50-inch machine guns. The two-seat version was to have an additional armament of a single 0.50-inch machine gun mounted in a remotely-controlled barbette situated at the end of each tail boom. During a meeting at Wright Field in May 1940, it was decided to drop the single-seater and proceed with the two-seat version, which was assigned the designation XP-58. In July 1940, it was concluded that the XP-58 would be underpowered with the Continental engines, and the decision was made to switch to a pair of 1800 hp Pratt & Whitney XH-2600-9/11 liquid-cooled engines. The re-engined XP-58 was given the company designation of Model 20-14, and revised specifications were issued by Lockheed on September 10, 1940. A second 20-mm cannon was added to the forward-firing armament. The tail boom guns were deemed to be highly impractical, and were replaced by a single remotely-controlled dorsal turret containing a pair of 0.50-inch machine guns. Estimated gross weight had crawled upward to 24,000 pounds, and estimated top speed had fallen to 402 mph. Range on internal fuel was anticipated to be 1600 miles.

However, scarcely a month after these revised specifications had been issued, Pratt & Whitney suspended development of the XH-2600 engine. The XP-58 was now without an engine. Attention focused on the XH-2470, the Continental XH-2860, and on the Pratt & Whitney R-2800, as possible choices for the XP-58 powerplants. Lockheed preferred the Pratt & Whitney R-2800 radial engine, and estimated that with these powerplants the XP-58 would have a a loaded weight of 26,000 pounds and a maximum speed of 418 mph at 25,000 feet. However, the USAAC considered this performance to be inadequate, and suggested that Lockheed turn to the experimental Wright XR-2160 Tornado forty-two cylinder, six-row engine offering a power output of 2350 hp. One advantage of this engine was that it had an extremely small frontal area. However, the Tornado engine was highly complex, and its development was fraught with problems from the start. Nevertheless, in March of 1941 the USAAC announced that it was going to go with the Tornado for the XP-58. Two months later, the USAAC issued an change order for the installation of cabin pressurization for the pilot and the aft-facing gunner, and for the addition of a remotely-controlled ventral turret to supplement the dorsal turret. The XP-58 was scheduled for delivery to the USAAF in August of 1942, and to meet this deadline the project team grew to a peak of 187 people by October of 1941.

In March 1942, Lockheed suggested that the USAAF order a second XP-58 prototype using Government funds. Since the Tornado engines were already experiencing serious delays and were now not expected to be delivered until the spring of 1943, Lockheed felt that there was sufficient time to redesign the second XP-58 machine in order to provide it with enough fuel capacity to increase the range to 3000 miles. The USAAF agreed to this request and indeed placed the order in May of 1942.

However, shortly thereafter, the USAAF began to go through a protracted series of flip-flops in their thinking about the ultimate mission for the XP-58. First, the USAAF suggested that the nose-mounted forward-firing armament should be changed to a 75-mm cannon with a 20-round automatic feeder plus a pair of 0.50-inch machine guns. This was an odd choice of armament for an escort fighter, so the USAAF began to think seriously of the XP-58 as a ground attack aircraft, the XP-58A. This in turn led to considerations of several different alternative configurations, including a two-seat attack aircraft with six forward-firing 20-mm cannon and a three-seat bomber with a bombardier in the nose, an enlarged central nacelle containing an internal bomb bay, and with or without the 75-mm nose cannon. In both the attack and bomber versions, the dorsal and ventral turrets were to be deleted, and unsupercharged engines were to be used.

It was soon realized that the last thing the USAAF need was another attack bomber. The Douglas A-26 Invader and the Beech A-38 Grizzly weres already in production, and it more than adequately filled all USAAF attack bomber requirements. Consequently, the USAAF decided that there was little point in trying to make the XP-58 into a low-level attack plane. The XP-58 program was then re-oriented back to its original role as a high-altitude aircraft designated the XP-58B However, this time it was to be bomber destroyer rather than an escort fighter. The turbosuperchargers and the dorsal and ventral turrets were put back on. The first prototype was to have four forward-firing 37-mm cannon, whereas the second was to have a 75-mm cannon and two 0.50-inch machine guns. Gross weight was now up to an astronomical 38,275 pounds, and top speed was down to 414 mph at 25,000 feet. Range was only 1150 miles.

By early 1943, the XP-58 program was in utter chaos because of the constantly changing Army requirements. In desperation, Lockheed recommended in January 1943 that only one prototype actually be built, and that it have interchangeable noses that would permit the fitting of either type of forward-firing armament. To make things even worse, the trouble-ridden Tornado engine program finally collapsed in February 1943, leaving the XP-58 without engines once again. Lockheed and the USAAF both agreed to switch to a pair of turbosupercharged Allison V-3420-11/13 twenty-four cylinder liquid-cooled engines, rated at 2600 hp for takeoff and 3000 hp at 28,000 feet.

With these Allison engines, the XP-58B was finally completed in June 1944, more than four years after its design had begun. When the XP-58B rolled out of the factory it was really only half-finished—no cabin pressurization equipment was provided, no forward-firing armament was installed, and dummy dorsal and ventral turrets were fitted in place of the real things. The flight tests were disappointing and the aircraft seemed destined for abandonment. By 1945, it was sitting neglected in the corner of an airfield and was more or less abandoned.

What happened next was amazing. Hughes Aircraft had designed a new reconnaissance aircraft designated the XF-11. This was a sleek, twin-engined aircraft that bore a startling resemblance to the Lightning series of fighters. It was fast, high-flying and almost impossible to maintain. This wasn’t helped by the eccentric behavior of Howard Hughes. In January 1945, the USAF confiscated all of the design and production data on the XF-11 along with both prototypes then under construction. Lockheed were called in (due to their experience with twin-boom aircraft) and given the job of producing a fighter version of the XF-11.

Lockheed went to work with a will, using the experience so painfully gained with the XP-58 to produce a new fighter that combined the best features of the XP-58 and the XF-11. The resulting aircraft looked very much like the XF-11 externally but was completely redesigned internally to ease production and maintenance. This aircraft was designated the XP-58C. It was powered by two R-3350 engines driving contra-rotating propellers. The XP-58C first flew in July 1946 and proved a much better aircraft than any of its predecessors. It was followed by the XP-58E that was essentially a service trials version of the design, armed with four B-20 20mm cannon closely grouped in its nose. The YP-58F followed and was essentially a modified XP-58E. Following service trials, the aircraft went into production as the F-58A Chain Lightning. Why the designation system reverted to an A suffix remains a mystery

Variants

Lockheed F-58A Chain Lightning

Following service trials, the aircraft went into production as the F-58A Chain Lightning. Why the designation system reverted to an A suffix remains a mystery. The F-58A was essentially identical to the XP-58F and production was just getting under way when The Big One ended World War Two. Only 73 F-58As had been built when production was paused dependant upon an assessment of post-war requirements.

Specifications of the F-58A

Performance: Maximum speed: 466 mph at 25,000 feet, cruising speed: 274 mph at 25,000 feet, initial climb rate: 3660 feet per minute, service ceiling: 44,400 feet, normal range: 2,250 miles, maximum range: 3,650 miles. Weights: 21,624 pounds empty, 39,192 pounds normal loaded, 43,000 pounds maximum. Dimensions: wingspan 70 feet 0 inches, length 49 feet 4 inches, height 16 feet 0 inches, wing area, 600 square feet. Armament was four 20mm B-20 cannon with 250 rpg.

Lockheed F-58B Chain Lightning

The Red Sun trials had shown that existing interceptors were incapable of engaging the B-36. Lockheed proposed a new version of the F-58A, drastically lightened and equipped with turbocharged R-4360 engines and had extended wings to improve high-altitude performance. They were given a contract to build 30 of these fighters, primarily for test and evaluation at Red Sun. They appeared in the 1950 Red Sun exercises and proved capable of intercepting the B-36 although they lacked the performance at those altitudes to form an effective defense. Nevertheless, the F-58B was considered a success and was ordered into limited production.

Specifications of the F-58B

Performance: Maximum speed: 456 mph at 35,000 feet, cruising speed: 254 mph at 25,000 feet, initial climb rate: 3360 feet per minute, service ceiling: 52,400 feet, normal range: 2,250 miles, maximum range: 3,050 miles. Weights: 19,624 pounds empty, 37,192 pounds normal loaded, 43,000 pounds maximum. Dimensions: wingspan 101 feet 0 inches, length 49 feet 4 inches, height 16 feet 0 inches, wing area, 983 square feet. Armament was four 20mm B-20 cannon with 250 rpg.

Lockheed F-58C Chain Lightning

The Lockheed F-58C essentially took the night-fighting equipment out of a P-49G and transferred it into a F-58B. Although the fighters available by 1951 had a very marginal capacity to intercept the B-36, they could only do so in clear weather. The F-58C was an attempt to produce an all-weather fighter that could fill the yawning defense gap. It, like its day-fighting sibling, was only marginally capable of intercepting a B-36 and by the time it entered service, the B-60 was already under test. Nevertheless, the F-58C was a viable stop-gap solution and entered production, gaining the distinction of being the last piston-engined fighter to be built for the USAF. The last F-58Cs were only withdrawn from service in 1958.


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